Re-roofing encompasses both primary membrane
replacement and replacement of the entire roofing assembly above
the structural deck.
Due to the unique nature of re-roofing, relief
from the Warranty Certificate standard may be requested. When
relief is requested, applications shall be made in a written
submission to the ARCA Warranty Ltd. Technical Committee. This
request for relief is termed a “Variance Request” and
must contain all pertinent information explaining why relief is
The Warranty Certificate standards, as itemized
in this manual, are applicable to re-roofing as well as new
construction, with the exception that the existing drainage slope
may be retained in a conventional membrane design if less than
Sheet metal flashings adhered to the primary
membrane shall be replaced with new materials. Base and cap
flashings may be reused provided they are in good condition,
fabricated to the Warranty Certificate standard, fit properly and
are not bitumen contaminated.
The Warranty Certificate can only be issued on
self-contained roof areas. Control joints may be required to create
a self-contained area when partial roofing system replacement is
carried out. Special attention to drainage provisions may be
Roof mounted equipment may need to be removed
and reinstalled to facilitate replacement of the roofing system
beneath them. Equipment mounted on properly constructed curbs of
sufficient height may not require removal.
A minimum clearance of 100mm (4”) shall be
maintained between the underside of service lines and the surface
of the completed roofing system.
When an existing roofing system is of a bitumen
type construction then care must be taken to ensure that the
bitumen materials do not come into contact with thermoplastic
Bitumen contaminated surfaces shall be covered
with an acceptable overlayment prior to membrane attachment.
In some instances there may be two (2) roof
systems one above of the other, over an existing roof area. Where
two (2) primary membranes are present, both primary membranes shall
Prior to reroofing, all damaged or deteriorated
decks and substrates shall be replaced or repaired with similar
To qualify for an ARCA 15 Year Warranty
Certificate, only new drains shall be installed equal in size to
existing roof drains.
TP-10.2 Primary Membrane
When considering an existing conventional
insulated roofing system for primary membrane replacement the
following factors require evaluation:
The effect that the lack of a vapour retarder may have had on
the failure of the existing membrane,
The type, condition and thickness of the existing insulation
and the amount of moisture that may have infiltrated the insulation
The existing roof deck type and its structural integrity if
moisture reached the deck.
The attachment of roofing system components to their existing
When membrane replacement is undertaken,
uncorrected defects hidden from view, such as wet insulation or
deteriorated deck, could jeopardize roofing system
Wet and damaged insulation shall be removed and
replaced with new insulation, to match the existing
Care must be taken to ensure all wet insulation
is located and replaced.
Under no circumstance shall a phenolic resin
insulation product be left in place or reused.
Existing of wood fiberboard, mineral
fiber/perlite fiber and stramit primary insulation shall not be
left in place or reused.
Existing polyisocyanurate, urethane, foamglass,
cork, expanded polystyrene and minimum 38mm (1-1/2") thick glass
fiber or polystyrene roof insulation may be reused when approved by
the membrane manufacturer. Care must be taken to ensure that the
existing primary insulation is adequately attached to the existing
vapour retarder membrane and structural deck.
When the primary membrane is being removed
from stramit or glass fiber insulation that have a facer, the
condition of the insulation facer after the tear off determines the
surface preparation method for the application of the new roof
membrane. When re-roofing over stramit the first layer of approved
coverboard must be mechanically fastened to the structural joist or
deck. If the first layer is fiberboard, then the second layer of
approved 12.7mm (1/2”) coverboard may be adhered or
mechanically fastened with screws and plates. When thermal
upgrading is required, the first layer of the secondary
insulation/coverboard may be substituted for/by the upgraded
insulation material. Attachment requirements remain the same.
TP-10.3 Roofing System
After tear-off the exposed substrate shall be
inspected for deterioration or damage and repairs undertaken prior
to the application of the replacement roofing system.
Control joints, parapets, curbs and roof/wall
junctions shall be adjusted to comply with the minimum height
requirements for new construction.
For conventional insulated designs, the
application of a vapour retarder is a requirement whether or not
the original roofing system contained a vapour retarder
An existing vapour retarder may be left in place
if well adhered. Any wet or damaged felt membrane shall be removed
and an additional one (1) ply of felt adhered with hot bitumen
shall cover the entire felt vapour retarder surface.
When primary membrane replacement occurs
over existing rigid glass fiber insulation, inspection of the
exposed insulation by an ARCA Accepted Inspector is required at the
time of tear off, for both rural and urban projects. Additionally,
if there is a history of leaking, the inspector shall perform
moisture meter or cut tests, one for each 1000 ft² of
insulation area. These quality assurance inspections are in
addition to the normal inspections required for Warranty